$D$-meson semileptonic form factors at zero momentum transfer in (2+1+1)-flavor lattice QCD

TL;DR

This paper computes $D$-meson semileptonic form factors at zero momentum transfer using lattice QCD with physical pion masses, enabling precise determination of CKM matrix elements $ vert V_{cs} vert$ and $ vert V_{cd} vert$.

Contribution

It provides the first lattice QCD calculation of $D o K$ and $D o \pi$ form factors at $q^2=0$ with physical pion masses and multiple lattice spacings.

Findings

Form factors calculated at zero momentum transfer.

Results enable improved CKM matrix element determinations.

Analysis includes continuum and physical mass extrapolations.

Abstract

We present a calculation of the $D\to K \ell \nu$ and $D\to\pi \ell \nu$ semileptonic form factors at $q^2=0$, which enable determinations of the CKM matrix elements $\lvert{V_{cs}}\rvert$ and $\lvert{V_{cd}}\rvert$, respectively. We use gauge-field configurations generated by the MILC collaboration with four flavors of highly-improved staggered (HISQ) quarks, analyzing several ensembles including those with physical pion masses and approximate lattice spacings ranging from 0.12~fm to 0.042~fm. We also use the HISQ action for the valence quarks. We employ twisted boundary conditions to calculate the form factors at zero momentum transfer directly. We use heavy-light-meson chiral perturbation theory modified for energetic pions and kaons, and supplemented by terms to describe the lattice-spacing dependence, to obtain preliminary results at the physical point and in the continuum limit.